Recently, since a so-called white LED (LED: light emitting diode) is adopted as a backlight of a liquid crystal display of a cellular phone, production of the white LED is dramatically increased. Here, a white LED package refers to a light emitting unit including a semiconductor light emitting element (LED), which is, for example, formed by arranging a lead frame inside a recessed portion formed on a white resin case so as to be exposed, attaching a semiconductor light emitting element to the lead frame exposed inside the recessed portion and electrically connecting thereof together and forming a sealing resin containing fluorescent bodies in the recessed portion so as to cover the semiconductor light emitting element. Hereafter, it is expected that the use of the white LED in the backlight of the liquid crystal display will spread other than in the cellular phones. Moreover, as the use in the backlight of the liquid crystal display increases, adaptation into other fields of illuminating is considered.
In the case of using the white LED in the backlight of the liquid crystal display, high efficiency of the package mounting the white LED is strongly demanded for obtaining a prescribed luminance for a large-sized screen with as little electric power as possible.
However, in the aforementioned white LED package, not all of light generated in a semiconductor light emitting element is effectively used, but there are some portions where the light is confined to the inside of the package and cannot come out. A sealing resin generally has a refractive index of 1.4 to 1.5 while the refractive index of air is 1, and therefore light incident with an angle equal to or less than a constant angle due to the difference in the refractive index is reflected and returned. It is said, on the assumption that a light emitting body (for example, a semiconductor light emitting element) exists at the center of a sphere, all the light emitted from the light emitting body is not reflected since the light is incident perpendicular to the boundary surface, thus providing the highest efficiency in light extraction. Accordingly, many light emitting units (packages) each provided by forming a hemispherical lens and disposing a light emitting body at the center thereof have been proposed. However, upon actually manufacturing a prototype of the light emitting unit, sufficient light emitting efficiency could not be obtained with such a configuration.
Further, as a conventional technique described in a gazette, there exists a light emitting unit in which a resin container is provided with a recessed portion having a bottom portion on which a metal lead portion for supplying electric power to a light emitting element is exposed and a wall portion that rises up from an edge around the bottom portion, where the light emitting element is attached to the bottom portion of the recessed portion to electrically connect the metal lead portion and the light emitting element, and the recessed portion to which the light emitting element is attached is sealed with a sealing resin that transmits light from the light emitting element (refer to Patent Document 1).